I. Field of the Invention
The present invention relates generally to reflecting image planes used in optical applications More particularly the present invention relates to a pixel compensated electro-optical display system. The display includes a light source, a pixel compensator, and a first surface mirror.
II. Description of the Prior Art
Image distortions are routinely encountered in typical video projection systems. This is because most video projection systems require, somewhere along the projection route, the use of a reflective image plane of some type to provide a compact system by reducing the total length needed for the image projection to be made. For example, in large-screen television projectors, a series of reflective surfaces are used to allow for the compact construction of the projection system itself. The significant distortions are caused by the fact that the object for example, the projected CRT image, and the projection screen are not themselves parallel. The same problem arises in any projection system that relies on a reflected image, such systems including television projection, high definition television projections, and in almost all audio-visual applications.
The problem of distorted video projections has traditionally been approached in such a way that requires the use of relatively complex lensing and optical systems. The image distortions that are introduced by the optical geometry of the typical projection system have not historically been of significant concern because the picture quality has generally been held to be acceptable. However, more lately, data and video projectors have been developed to specifically display computer generated video information. In such applications, the video image distortions are not merely annoying, but are, in fact, critical flaws in such projection systems.
Typical distortions encountered in projection television systems include non-uniform focus, keystone distortion, and vertical and horizontal non-linearity. Each of these distortions results from the fact that the image source, that is, the projector and the display screen, are not parallel. This occurs where a projector image source is off the central optic axis and is known as horizontal displacement. Another possibility is where the axis of the projector is tilted with respect to the screen and this is called vertical displacement (See "Image Distortions in Video Projection", Dennis W. Vance, Vertex Video Systems publication) Both horizontal displacement and vertical displacement exist in the typical 3-tube color projecting unit. Such displacements result in the distortions mentioned above.
The first of these distortions, non-uniform focus, results from the non-horizontal placement of the projector with respect to the screen because only one part or the other of the image on the screen may be focused while the other remains out of focus. This is true because the focal length between the projector and the image is not constant. Conventionally, non-uniform focus has been corrected by using a fairly complex system of lenses disposed between the projector and the screen.
The two remaining types of distortions, keystone distortion and distortions related to non-linearity, are the result of image geometry. This is based on the fact that a projector and an image screen, when not parallel, result in magnification of the image being varied along the direction of the tilted plane. This distortion still remains, even after the interdisposition of a lens between the projector and the screen. Two types of distortions result from the magnification problem, the first of which is called keystone distortion and the second of which is called vertical non-linearity Keystone distortion results in variation of the horizontal magnification, while vertical non-linearity distortion results in variation in the vertical magnification.
Traditionally, efforts to correct these distortions have been made both electronically and optically. Electronic corrections include the pre-distorting of the primary image and this approach has been taken typically where CRT's and light-addressed light valves are employed. The modification of the optical system has conventionally been taken where matrix-addressed light valves are employed The correction of the distortions is extremely expensive and often produces enormously complex electronic and optical corrections systems. This is because the conventional approach has been to correct not the projection system, but the optics themselves.